FullStack .NET Developer (React)

🏢 OPTIVEUM sp. z o.o. · all OPTIVEUM sp. z o.o. jobs

📍 Poland

💰 PLN 18,000 - 25,000 / annual

📅 Posted 2026-08-20 · via Himalayas

🏷 Fullstack-Development,.NET-Development,Frontend-Development,Software-Engineer,React,Backend-Development,Fintech-Development,Senior-Full-Stack-Engineer-(.NET-React),Senior-.NET-Full-Stack-Developer,Senior-.NET-Full-Stack-Engineer

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About Optiveum and our Client

Optiveum is a boutique talent advisory firm. We help our clients build high-performance technology teams that move the needle.

We are currently looking for a Senior FullStack .NET Developer for our client—a fast-growing US-based leader in the Financial Technology sector . With a major engineering hub in Warsaw , they are blending American innovation and "move-fast" culture with top-tier Polish engineering talent. You’ll be joining an environment that skips the bureaucracy in favor of high ownership, architectural excellence, and a product-first mindset.
The Role

As a Senior FullStack Engineer, you aren’t just executing tickets; you are a product builder . You will bridge the gap between robust, high-scale backend services and modern, highly interactive user interfaces. This role is perfect for someone who thrives in a fast-paced US tech culture, enjoys solving complex distributed systems puzzles, and cares deeply about delivering a world-class User Experience (UX).
Your Responsibilities

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Full-Scale Development: Own features end-to-end, from database schema and API design to the final React component.

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Architecture & Scale: Contribute to the evolution of a Cloud-Native microservices architecture on Azure, designed to handle global traffic.

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Engineering Excellence: Maintain high standards (SOLID, Clean Code, Design Patterns) while maintaining the velocity needed for a competitive US market.

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Frontend Leadership: Drive the development of responsive, high-performance web applications using React.

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Global Collaboration: Partner closely with US-based Product Managers and Stakeholders to translate vision into scalable technical reality.

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Mentorship: Lead by example through Code Reviews and knowledge sharing, helping elevate the Warsaw engineering hub.

Requirements

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Backend Expertise: 5+ years of experience in .NET (.NET 6/8+) and C#. Expertise in building RESTful APIs and event-driven architectures.

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Frontend Mastery: Solid experience with React and TypeScript . Familiarity with state management (Redux, Zustand, or React Query).

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Cloud-Native Mindset: Practical experience with Azure (App Services, Functions, Service Bus, Cosmos DB/SQL).

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Database Knowledge: Strong skills in SQL Server and Entity Framework Core.

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Modern DevOps: Hands-on experience with Docker, Kubernetes, and CI/CD pipelines (Azure DevOps/GitHub Actions).

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Language: Excellent English (C1) – essential for daily collaboration with the US team.

Nice to Have

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Experience in high-growth FinTech, WealthTech, or high-frequency trading environments.

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Knowledge of testing frameworks (xUnit, Jest/Cypress).

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Familiarity with Web Performance optimization and Accessibility (WCAG).

What We Offer

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US Tech Culture: A transparent, high-growth environment that values "radical candor," innovation, and taking initiative.

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Professional Growth: Access to the latest tech—we operate on the "bleeding edge" of .NET and React.

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Modern Warsaw Office: A vibrant, well-located hub for collaboration, combined with a flexible hybrid/remote policy.

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Competitive Compensation: 18.000 - 25000 PLN B2B

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Global Scale: Your code will power mission-critical systems used by financial professionals and institutions across the US and globally.

Originally posted on Himalayas

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